F4 error, defrost heater does not energize and evaporator ices up repeatedly.

Safety: Unplug the freezer and allow any ice to melt before testing the heater. Water and electricity are a dangerous combination.

• Access the evaporator and heater: Remove the internal rear panel to expose the evaporator. The defrost heater is usually a metal or glass-encased element clipped beneath or around the evaporator.
• Inspect visually: Look for breaks in the heater element, burnt spots, or melted connectors.
• Test heater resistance: Disconnect the heater wires and measure resistance across the element. Typical values are between 50–300 Ω depending on design. An open circuit indicates a failed heater.
• Check thermal fuse (if fitted): Some Hoover models include a thermal fuse in series with the heater. Test for continuity; replace if open.
• Inspect wiring: Follow the heater wires back to the harness and PCB, checking for burnt or brittle insulation.
• Replace faulty components: Install a new defrost heater and/or thermal fuse as required, using Hoover-approved parts. Ensure all clips and insulation are refitted correctly.
• Reassemble and test: Refit the evaporator cover, restore power, and monitor over several days to confirm normal defrosting and that F4 does not return.

Warning: If the heater and wiring are good but the heater never receives power, the main PCB defrost relay may be faulty and should be checked by a technician.